Biodegradable resin composition

ABSTRACT

This invention provides a biodegradable resin composition and a biodegradable molding using the same and in particular, it not only have satisfactory biodegradability, processability and properties required for biodegradable resins by comprising cellulose diacetate as a main component but also can lower manufacturing costs and prevent environmental contamination by preparing the biodegradable resins by reusing a cause factor of environmental contamination.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a biodegradable resin composition and abiodegradable molding using the same and more particularly, it relatesto a biodegradable resin composition comprising cellulose diacetate as amain component, which can not only satisfy the biodegradability,processability and properties required for a biodegradable resin butalso lower manufacturing costs and prevent environmental contaminationby producing the biodegradable resin by reusing a cause factor ofenvironmental contamination and a biodegradable molding using the same.

2. Description of Related Art

As plastics are light and strong and they are easy to be processed andnot easily degraded, their consumption from industrial materials todisposable products and wrapping materials is continuously increasing.Hard wastes including such plastics are disposed by landfill orincineration after their use, or reused by recycling them. However, thedisposal of wastes by landfill, incineration, etc. gives rise toenvironmentally severe damage. Accordingly, to solve the environmentissue, various biodegradable plastics that keep their function andstructure during their use but can be degraded into water and carbondioxide by microorganism once wasted are being produced.

For example, U.S. Pat. Nos. 5,234,977, 5,256,711, 5,264,030, 5,292,782,5,334,634, 5,461,093, 5,461,094, 5,569,692, 5,616,671, 5,696,186,5,869,647, and 5,874,486 disclose methods of preparing biodegradableplastics by mixing a starch which is inexpensive and easilybiodegradable with common resins such as polyethylene, polypropylene andpolystyrene, and polyester-based matrix resins. However, as the starchis added, a plasticizer is to be added, which causes discoloring and badfume during processing and the properties of the plastics are remarkablydeteriorated.

Further, U.S. Pat. Nos. 4,133,784 and 4,337,181 disclose methods ofpreparing films by adding pregelatinized starches to ethylene-acrylicacid copolymers. However, the ethylene-acrylic acid copolymers areexpensive and the properties of the produced films are extremely fragilefor practical use, and their biodegradability is not good.

Further, U.S. Pat. Nos. 5,254,607, 5,256,711 and 5,258,430 disclose theuse of a pregelatinized starch, but they require a separate apparatusfor adding water and a plasticizer in a large amount so as topregelatinize starch and also, the degradability of the ethylene-vinylalcohol copolymers which are synthetic resins used to increaseproperties and dimension stability has not been verified.

Also, Korean Patent Laid-Open Nos. 1994-0011542, 1994-0011556, and1994-0011558 attempted reaction extrusion by use of an organic acidcatalyst and binding agent to induce the chemical binding of starch andpolyethylene. However, unreacted coarse monomers are likely to remain,and in the case that the content of the starch is more than 30%,mechanical properties are remarkably reduced, and the polyethylene whichis used as a matrix resin is not degraded and remains.

Hence, researches about methods of preparing biodegradable resins usingcellulose derivatives have been conducted and especially, the researchesabout the biodegradable resins using cellulose acetate among thecellulose derivatives have been mainly performed.

The cellulose acetate, a conversion form into an acetic ester ofcellulose, has been known to be inherently biodegradable but in fact,its biodegradability is not good. Thus, although molding productscomprising the cellulose acetate are laid under the grounds, theymaintain the prototype of the molding products until 1 or 2 years and ittakes considerably long time for the molding products to be completelybiodegraded. Also, the molding products are sometimes landfilled aswastes, or left in nature environment, not being recovered as wastes.

Accordingly, researches about methods for improving the biodegradabilityof the cellulose acetate are in progress. Japanese Patent Laid Open No.6-199901 discloses a method of regulating the biodegradability of thecellulose acetate by adding an acid compound having a higher aciddissociation constant than acetic acid to the cellulose acetate.However, in this method, at the point when the acid compound is added tothe cellulose acetate, the cellulose acetate is chemically hydrolyzed bythe influence of the acid compound and this hydrolysis reactiongenerates acetic acid, which gives strong acetic acid odor to thecellulose acetate products.

Therefore, studies about methods of preparing biodegradable plasticsusing different kinds of cellulose derivatives other than the celluloseacetate have been incessantly conducted and more progressive studies arein need.

SUMMARY OF THE INVENTION

In order to solve the problems of the prior arts, it is an object of theinvention to provide a biodegradable resin composition comprising acellulose (di)acetate as a main component, which satisfies thebiodegradability, processability and properties required for abiodegradable resin and from which acetic acid odor is removed, and abiodegradable molding using the same.

Also, it is another object of the invention to provide a biodegradableresin composition which can lower the manufacturing costs of thebiodegradable resin composition to be produced and prevent environmentalcontamination in advance by reusing a cause factor inducingenvironmental contamination and a biodegradable molding using the same.

It is still another object of the invention to provide a biodegradableresin composition capable of preventing environmental contaminationbecause the container is degraded under the ground or in the air withina short period when landfilled after its use, a method of preparing abiodegradable molding using the same and the biodegradable molding.

To achieve the aforementioned objects, the present invention provides abiodegradable resin composition comprising a cellulose diacetate as amain component.

Preferably, the molecular weight of the cellulose diacetate is 10,000 to500,000.

Also, more preferably, the biodegradable resin composition comprises:

a) 50 to 90 parts by weight of a cellulose diacetate; and

b) 10 to 50 parts by weight of a plasticizer.

Further, the invention provides a biodegradable molding prepared bykneading and extruding the biodegradable resin composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing of the biodegradability of a biodegradablefilm prepared by using an embodiment of the invention comprisingcellulose diacetate, comparing with that of cellulose which is astandard material.

FIG. 2 is a graph showing the biodegradability of PLA which is acommonly used biodegradable material, comparing with that of cellulosewhich is a standard material.

DETAILED DESCRIPTION OF THE INVENTION

This invention is further described in detail.

The inventors found that a cellulose diacetate can be biodegraded and ithas a remarkably low melting point and thus has an excellentprocessability while possessing superior properties and accordingly,they have completed the invention.

The biodegradable resin composition of the invention is characterized bycomprising a cellulose diacetate that is a biodegradable resin, as amain component.

Preferably, the biodegradable resin composition of the inventioncomprises a cellulose diacetate and plasticizer, and biodegradablemoldings can be prepared by evenly mixing the biodegradable resincomposition and kneading and extruding the mixed composition.

The cellulose diacetate is contained in the biodegradable resincomposition preferably in an amount of 50 to 90 parts by weight. Withinthe above ranges, satisfactory processability as a biodegradable resincomposition as well as the properties of moldings can be obtained.

Preferably, the cellulose diacetate can be obtained from a wastecigarette filter which is a cause factor of environmental contamination,and the manufacturing costs of the biodegradable resin compositions canbe remarkably lowered by preparing the biodegradable resin compositionsby recycling the cellulose diacetate of the waste cigarette filters andenvironmental contamination can be prevented in advance.

The plasticizer used in the invention makes molding, injection, etc.easy when the biodegradable moldings are prepared and it improves glasstransition temperature (Tg), tensile strength, Young's modulus, etc. ofthe cellulose diacetate.

For the plasticizers, triacetin (TA), triethyl citrate (TEC), orglycerin can be suitably used, epoxidized soybean oil (ESO) as asecondary plasticizer can be added thereto and preferably, it ispreferable to use triacetin.

The plasticizer is contained in the biodegradable resin composition ofthe invention preferably in an amount of 10 to 50 parts by weight, andthe above range is preferable in aspect of the easiness of molding andinjection when the moldings are prepared.

The biodegradable resin composition comprising the above components mayfurther comprise clay minerals such as montmorillonite and bentonite,additives such as a degradation catalyst or processing aid, etc. ifnecessary and their amount is preferably 0.1 to 10 parts by weight.

For the catalysts, a latent heat catalyst can be used to cause the ringopening polymerization of epoxidized soybean when the epoxidized soybeanis contained as a plasticizer.

The clay minerals have excellent hygroscopic property due to theirlaminated structure and accordingly, they render the moldings preparedwith the biodegradable resin composition of the invention to be readilydegraded even in the water. In particular, the montmorillonite ispreferably used as a clay mineral.

Also, when the clay minerals are used in the biodegradable resincomposition of the invention, it is preferable to mix the clay mineralswith the plasticizer and disperse them using an ultrasonic machinebefore they are added to the biodegradable resin composition.

Further, the invention may further comprise a natural vegetable fiber asa filling agent within the biodegradable resin composition in thepreparation of the biodegradable resin composition. Specific examples ofthe natural vegetable fiber are coconut fiber, hemp fiber, ramie fiber,sisal fiber, henequen fiber, pineapple leaf fiber, cotton fiber, coierfiber, rice straw, etc. and it is preferable to have an average diameterof 10 to 500 μm or so. Also, the filling agent is contained preferablyin an amount of 1 to 50 parts by weight of 100 parts by weight of thebiodegradable resin composition, and in this case, it is advisable tomaintain the content of the plasticizer in at least 10% by weight of thebiodegradable resin composition. If the filling agent is used,mechanical strength can be complemented and the use of the naturalvegetable fibers that are inexpensive can much lower the manufacturingcosts of the biodegradable resin composition.

Further, the invention provides a biodegradable molding characterized inthat it is prepared by kneading and extruding the biodegradable resincomposition comprising the aforementioned components.

For the kneading and extrusion, conventional methods used to knead andextrude biodegradable resin compositions can be applied and for example,a twin screw extruder or batch mixer can be used.

Preferably, the temperature during the kneading process is 25˜120° C. asthe melting point of the cellulose diacetate is low and more preferably,it is 25˜100° C.

Also, after kneaded at the above temperature, it can be molded intomoldings preferably at the temperature of 160˜220° C. using a commonextruder.

The biodegradable moldings prepared by the aforementioned method can beapplied to films for semiconductor packaging, disposable products suchas a variety of containers, cups, spoons, forks, knives, toothbrushesand straws, paper cups, melty coatings such as paper coatings for themanufacture of paper plates, mulching films, agriculture and gardeningsupplies such as plant ports, clips, etc. garbage bags, compost bags,shrink wrap films, wrapping films, medical supplies such as syringes foranimal injection, mouthpieces for endoscope, modifiers for hardbiodegradable plastics, golf tee, fish net, fishing line, bottles, avariety of stationery and so on.

The biodegradable resin composition in accordance with the invention ismelted at a melting point remarkably lower than the melting pointrequired in the manufacture of cellulose derivatives used as a substanceof prior biodegradable plastics so that it is easy to be prepared intomoldings and at the same time, it has properties equal to those of themoldings prepared by using the prior biodegradable resins. In addition,it can in advance prevent environmental contamination by reusing a causefactor of environmental contamination and remarkably lower themanufacturing costs of the biodegradable resin compositions. Also, asthe biodegradable moldings prepared by using the biodegradable resincompositions of the invention can be degraded under the ground or in theair within a short period when landfilled after their use, they have anadvantage in that they can prevent environmental contamination.

For better understanding of the present invention, preferred embodimentsfollow. The following examples are intended to merely illustrate theinvention without limiting the scope of the invention.

EXAMPLES Example 1

After 70 parts by weight of cellulose diacetate having a molecularweight of 202,332 (Eastman Co., Ltd.), and 30 parts by weight oftriacetin (Mw. 218.21, major component C₉H₁₄O₆), Dae Shin Chemical Ind.Co., Ltd.) as a plasticizer were evenly mixed, the mixture was kneadedfor 3 hours at the temperature of 100° C. and melted in Haake rheocordsystem of 200° C. thereby to prepare a blending mixture.

Examples 2 to 8 and Comparative Examples 1 to 6

With the exception that the compositions and ratios as shown in Table 1below were used, blending mixtures were prepared by carrying out thesame method as above Example 1. TABLE 1 Cellulose (Parts by PlasticizerWeight) TA TEC GC ESO BET EX. 1 CDA¹ 70 30 EX. 2 CDA¹ 80 20 EX. 3 CDA¹80 20 EX. 4 CDA¹ 80 20 EX. 5 CDA¹ 80 10 10 EX. 6 CDA² 80 20 EX. 7 CDA²70 20 10 EX. 8 CDA³ 80 20 EX. 9 CDA³ 70 30 COM. EX. 1 CA 90 10 COM. EX.2 CA 80 20 COM. EX. 3 CA 70 30 COM. EX. 4 pure PP COM. EX. 5 pure PLANoteCDA¹: Cellulose (Di)Acetate(Mn ca. 202,332 g · mol⁻¹, 54.5 wt. % acetylcontent, Tg 188° C., Eastman Co., Ltd)CDA²: Recycling fabric CDA (SK)CDA³: Recycling fiber CDA (SK)CA: Cellulose acetate(Mn ca. 50,000 g · mol⁻¹, 39.7 wt. % acetylcontent, Tg 188° C., Aldrich Co., Ltd.)PP: Polypropylene (grade H1500, Hyundai)PLA: Polylacetic acid (Mn 83,000 g · mol⁻¹ , Mw 153000 g · mol⁻¹Cargill-Dow Co., Ltd.)TA: Triacetin(Mw. 218.21), Dae Shin Chemical Ind. Co., Ltd.TEC: Triethyl citrate(Mw. 276.29), Aldrich Co., Ltd.ESO: ShinDongBang CoroperationGC: Glycerin

The blending mixtures prepared by melting the biodegradable resincomposition in Haake rheocord system in Examples 1 to 9 were extrudedfor 10 minutes at the melting points of the blending mixtures usingCarver laboratory press equipped with a temperature control devicethereby to prepare initial films having a width of 10 cm, a height of 10cm and a thickness of 300 μm. The prepared films were cut into oneshaving a width of 0.5 cm and a height of 4 cm and their glass transitiontemperature and modulus were measured by Dynamic Mechanical Analyzer.The results are shown in Table 2 below. TABLE 2 Glass transitiontemperature (Tg) and Young's modulus measured from MDA Young's modulusEX./COM. EX. Tg (° C.) (GPa) EX. 1 97 1.50 EX. 2 108 1.55 EX. 3 138.51.72 EX. 4 146.9 1.64 EX. 5 141.9 1.91 EX. 6 89.9 1.34 EX. 8 92.8 1.34COM. EX. 2 206.3 2.51

As shown in Table 2 above, the working Examples of the invention hadremarkably lower Tg and Young's modulus than Comparative Example inwhich cellulose acetate was used and thus they could be very easilyprocessed.

In addition, to measure mechanical properties of the working Examples ofthe invention and Comparative Examples, tensile specimen were preparedaccording to ASTM D1708 and ASTM D638, wherein the injection pressurewas 750-900 psi, injection time was 3 seconds, the temperature ofcylinder was 180-200° C. and cycle time was 2 min. The mechanicalstrength of the films prepared above was measured by the machine namedLR30K-plus from LLOYD, Inc. 10 Specimen in each example were fabricatedand then tested. The average value was taken and the results are shownin Table 3 below. TABLE 3 Young's Tensile Strength Elongation modulusEX. (MPa) (%) (MPa) EX. 1 72 8 2300 EX. 2 131 8 3671 EX. 4 90 5 2964 EX.9 73 6 2254 COM. EX. 5 84 5 2633

As shown in Table 3 above, the biodegradable resin compositions of theinventions showed properties similar to Comparative Example 5 in whichthe prior biodegradable resin was used.

Also, in order to examine the biodegradability of the biodegradableresin compositions of the invention, the biodegradable resin compositionof Example 2 was subject to experiment according to KS M 3100-1 (ISO14855) provision, and the biodegradability test was carried out incomposting conditions. The composition of Comparative Example 5 wastested likewise. As of cellulose which is a standard material andExample 2 and Comparative Example 5, their aerobic biodegradability andcollapse rate were measured in the composting conditions and thequantity of the generated carbon dioxide was measured by titration.

FIG. 1 showed the biodegradability of Example 2 of the invention andcellulose which is a standard material over time and FIG. 2 showed thebiodegradability of Comparative Example 5 and the cellulose which is astandard material over time.

As shown in FIG. 1 and FIG. 2, the biodegradable resin composition ofthe invention showed biodegradability almost equal to that ofComparative Example 5 wherein the commonly used biodegradable resincomposition was used.

The biodegradable resin composition in accordance with the invention canremarkably lower the manufacturing costs when compared with thecellulose acetate which has been used as biodegradable plasticmaterials, can prevent environmental contamination by reusing the causefactor of environmental contamination, remarkably improves theproperties, is easy to be prepared into moldings at a low temperaturedue to its low melting point, and has considerably improved propertieswhen compared with prior biodegradable moldings using starch.

1. A biodegradable resin composition comprising a cellulose diacetate asa main component.
 2. The biodegradable resin composition according toclaim 1 wherein the cellulose diacetate is an ethyl cellulose having amolecular weight of 10,000 to 500,000.
 3. The biodegradable resincomposition according to claim 1 wherein the biodegradable resincomposition comprises: a) 50 to 90 parts by weight of a cellulosediacetate; and b) 10 to 50 parts by weight of a plasticizer.
 4. Thebiodegradable resin composition according to claim 1 wherein theplasticizer is selected from the group consisting of triacetin (TA),triethyl citrate (TEC), glycerin and a mixture thereof.
 5. Thebiodegradable resin composition according to claim 1 wherein thecellulose diacetate is obtained from a waste cigarette filter.
 6. Thebiodegradable resin composition according to claim 1 wherein thebiodegradable resin composition further comprises a clay mineral,degradation catalyst or processing aid.
 7. The biodegradable resincomposition according to claim 1 wherein the biodegradable resincomposition further comprises a natural vegetable fiber.
 8. Abiodegradable molding prepared by kneading, extruding and injecting thebiodegradable resin composition of claim
 1. 9. The biodegradable moldingaccording to claim 8 wherein the biodegradable molding is a film forsemiconductor packaging, container, cup, spoon, fork, knife, toothbrush,straw, paper cup, paper coating for the manufacture of paper plates,mulching film, plant port, clip, garbage bag, compost bag, shrink wrapfilm, wrapping film, syringe for animal injection, mouthpiece forendoscope, modifier for hard biodegradable plastics, golf tee, fish net,fishing line, bottles or stationery.